John Wesley on Numbers 24:20

He looked on Amalek - From the top of Pisgah, which was exceeding high, and gave him the prospect of part of all these kingdoms. The first - Heb. the firstfruits; so called either, because they were the first of all the neighbouring nations which were embodied together in one government: or, because he was the first who fought against Israel and was vanquished by them. That victory was an earnest and first - fruit of the large harvest of victories which the Israelites should in due time get over all their enemies. He shall perish for ever - He began with God and with Israel, but God will end with him, and the firm purpose of God is, that he shall be utterly destroyed; so that Saul lost his kingdom for not executing this decree, and God's command pursuant thereunto.